Plastic Bag, in Particular FFS Bag, and Method and Device for Producing and Filling a Bag

ABSTRACT

The invention relates to a plastic bag, in particular an FFS bag, comprising a first wall and a second wall, which are joined to each other by means of side edges or side folds and by means of bottoms and which bound a bag interior, wherein at least one bottom comprises a weld seam, which extends between the side edges and touches the side edges, and venting openings in the first and/or in the second wall for venting the bag interior, characterized in that at least one channel is provided on the outside of at least one wall, which channel covers the venting openings and is formed by at least two parallel fastening strips and by a cover strip, wherein the cover strip likewise comprises venting openings and wherein the shortest path between the parallel fastening strips along the cover strip is longer than the shortest path along the at least one wall between the parallel fastening strips or the cover strip and/or the parallel fastening strips consist of stretchable material.

The invention relates to a plastic bag according to the preamble of Claim 1 and to a method according to the preamble of Claim 9 and to a device according to the preamble of Claim 12.

FFS bags are bags which are as a rule manufactured at first inside a device, then filed and finally closed. The term FFS bags denote bags here which are filled with a filling material with a weight of at least 5 kg (filling weight). Bags with a filling weight of at least 25 kg are even the rule. The hose web used is often, but not exclusively, provided with side folds. Therefore, the bags manufactured from it have a first wall and a second wall which are connected to one another by side edges or side folds as well as by bottoms. This bounds a bag interior. Of course, in the case of existing side folds, they are also connected by side edges to the walls.

During the filling of these bags, which have already been provided with a bottom, at this point in time, there is the problem that the air which was carried into the interior with the filling material must escape in order to keep the volume of the filled bag as small as possible. Furthermore, air remaining in the bag can cause the bag to easily burst if it falls unintentionally from a certain height on the floor. In addition, the ability to stack these bags can be reduced. Traditional bags are therefore provided with venting openings which can be, for example, micro perforations so that air but no filling material can exit. WO 2007/087965 discloses two channels running in a longitudinal direction and with a fluid connection which represent a labyrinth venting. The venting openings can be designed to be comparatively large here. Nevertheless, the necessary venting performance is often insufficient for known bags because in the previous years the filling performance of the generic FFS systems for bags with more than 5 kg of filling weight has steadily risen.

Therefore, the present invention has the problem of suggesting bags with a higher venting performance and a method and a device for manufacturing and filling these bags.

The problem is solved according to the invention by all the features of Claim 1.

Accordingly, the invention provides for a plastic bag, in particular for an FFS bag, comprising a first wall and the second wall which are connected to one another by side edges or side folds as well as by bottoms and bound a bag interior, wherein at least one bottom comprises a weld seam which runs between the side edges and contacts them, and comprises vent openings in the first and/or in the second wall for venting the bag interior, that at least one channel is provided on the outside of at least one wall which channel covers the vent openings and which is formed at least by two parallel fastening strips and a cover strip, wherein the cover strip also comprises openings and wherein the shortest path between the parallel fastening strips along the cover strip is longer than the shortest path along the at least one wall between the parallel fastening strips or the cover strips and/or the parallel fastenings consist of stretchable material.

The sides or surfaces of the first wall and of the second wall which face the bag interior can also be designated as inner sides, and the sides facing away from the bag interior can be correspondingly designated as outer sides. Such a bag has a direction of extension running in the direction of the largest longitudinal axis, wherein it lies parallel to the outer edges. As already mentioned, the first and the second wall are connected to one another by two edges and can be formed in one piece. The walls can be formed by a hose running transversely to the direction of extension or can be formed to a hose from a flat web forming a longitudinally running overlapping area. Side folds can be placed in such a hose, wherein the first wall is then connected by an outer edge to a first position of the side fold, and the second wall is connected by an outer edge to a second position of the side fold. One first position of the side fold, respectively, is connected to a second position of the side fold, respectively, by an inner edge. Outer edges and inner edges advantageously run parallel to the direction of extension of the hose or of the later bag. The width of a position of the side fold defines the so-called depth of the side fold.

The at least one cover strip is fastened by at least two fastening strips which are fastened parallel to the direction of extension on an outer side of at least one wall and as a result forms a channel together with the wall. The cover strip preferably covers venting openings introduced in the one wall. The invention furthermore provides that the shortest path between the parallel fastening strips along the cover strip is longer than the shortest path along the at least one wall between the parallel fastening strips or the covers strips. In other words, the cover strip has a greater width in the distance encompassed by the fastening strips when the wall is plane, that is that is lies on a single plane. In a preferred embodiment the cover strip comprises at least one folding edge along which its inner wall is folded back on itself and/or the cover strip is fastened by a fastening strip by its inner surface on the at least one wall and is fastened by the other fastening strip by its outer surface on the at least one wall.

The cover strip can be part of a flat web and is preferably formed in this case by the overlapping area of the two edges. In this case, the wall on which the cover strip is fastened is formed from two parts which are fastened to one another by a fastening strip, wherein this fastening strip is at the same time the one fastening strip of the cover strip.

However, the cover strip can also be a separate strip which is fastened on one of the two walls. Even several cover strips are basically conceivable.

In an alternative embodiment of the invention, even a separate strip can be fastened on the inner side of the at least one wall in which strip at least one venting opening is then introduced. In this case, the area of the at least one wall which is located between the fastening strips assumes the function of the cover strip, as was described in conjunction with the above embodiments. Therefore, it is provided in this instance that the shortest path between the parallel fastening strips along the cover strip is shorter than the shortest path along the at least one wall between the parallel fastening strips.

In another alternative of the invention, the shortest path between the parallel fastening strips along the cover strip is just as long as the shortest path along the at least one wall between the parallel fastening strips, but in this case the cover strip comprises elastic material, i.e., the shortest path between the two fastening strips along the cover strip can be lengthened.

The cover strips can be formed by a material such as, e.g., cold adhesive, hot adhesive (hot melt), extrudate or other additions which achieve a fastening effect. However, such fastening strips can be produced without an addition of material such as, e.g., by hot-air sealing or hot-air welding, by contact welding, by ultrasonic welding or similar methods. The fastening strips preferably have no interruptions but can alternatively also have small interruptions through which air can exit out of the channel into the environment. Such interruptions can be equal alternatives to the venting openings in the cover strip.

The invention solves the above-indicated problem in the following mode of operation. During the filling of the filling material into the bag, air is constantly introduced into the bag whether desired or not. This air can now enter into the channel in a bag according to the invention through the venting openings introduced into the bag wall. The venting openings can be large in order that the air can escape in a very short time out of the inner chamber of the bag. As a result of the special nature and fastening of the cover strip, the channel can become distinctly larger under the influence of the air and therefore receive a large volume of air. The air stored in the channel can now be slowly given off to the environment via the venting openings in the cover strip and/or via the interruptions in the fastening strips, wherein as a result of the slow discharging, low or hardly any of the filling material of the bag is entrained and therefore remains almost completely in the bag even if a small part of the filling material remains in the channel. Therefore, the bag can be filled in this manner at a very high speed without the environment of the bag filling station becoming contaminated with filling material. The venting of the channel should then not take very much time even after the bag has already been closed.

In a preferred embodiment of the invention, the shortest path between the parallel fastening strips along the cover strip is at least 3% longer than the shortest path along the at least one wall. In this case a sufficient venting performance is made available, wherein the material used is efficiently managed at the same time. Furthermore, it is advantageous if the shortest path between the parallel fastening strips along the cover strip is at the most 20% and in particular at the most 10% longer than the shortest path along the at least one wall.

It is also advantageous if a layer of a filter material is provided inside the channel. The filter material is arranged here in such a manner that the air must pass through it in order to be able to pass to the venting openings in the cover strip or to the interruptions of the fastening strips. The filter material is preferably fastened here by a circumferential fastening seam on the cover strip and/or on the at least one wall and/or on the fastening strips. Such a filter material can be a fibrous substance, for example paper, or a plastic fleece. The advantage of this embodiment is that the filling material is retained by the filter material in particular when a dusty filling material is concerned. In a further development the filter material can even be moisture-absorbent so that moisture entering through the venting openings can be absorbed by the filter material so that the filling material is protected as well as possible from moisture.

In another advantageous embodiment of the invention a layer consisting of a filter material is provided in the bag interior, wherein the filter material covers the venting openings of the at least one wall. Even in this case it is advantageous if the filter material, which is present as a piece of material, is fastened by a circumferential connection seam on the at least one wall so that no air can flow through between the wall in the filter material. The connection seam surrounds all venting openings. Even this method prevents filling material from passing into the environment.

An advantageous further development provides that the air permeability of the venting openings in the at least one wall is greater than the air permeability of the cover strip. To this end, the venting openings of the cover strip can be produced by a needle perforation. In this case, holes with a maximum diameter of 0.8 mm are produced. Microperforations, for example, with a density of 5 to 30, in particular 13, venting openings per square centimeter (cm³), and nanoperforations, for example with a density of 50 to 100, in particular 64 venting openings per square centimeter (cm³) can often be distinguished from each other in combination with or also independently of the needle perforation. The perforations can be produced, for example, with substantially conical needles or with substantially cylindrical needles. The venting openings in the at least one wall can be readily introduced by the introducing of small steps. To this end, a cutter block is preferably used. The advantageous effect of these previously cited features is that as a result of them a very rapid final ventilation of the bag interior can take place, wherein the air can then be stored in the channel in order to slowly discharge it into the environment. This can effectively prevent that filling material is discharged with the exiting air into the environment. An exiting of filling material can be avoided, particularly with the micro- or nanoperforations described above.

Another advantageous embodiment of the invention provides that the venting openings of the cover strip are at a distance from the at least one bottom by a maximum of one half a bag length, in particular a maximum of one third of the bag length. In particular, the at least one bottom denotes the lower bottom when the bag is substantially vertically positioned during the filling. This is, at the same time, the bottom which is manufactured at first inside an FFS machine. In this case, a labyrinth-like guidance of the air introduced with the filling material is achieved, especially when the venting openings introduced into a wall are arranged on the upper end of the bag which is not yet closed during the filling. In this manner, parts of the filling material which pass into the channel do not find any direct path in the direction of the environment so that a contamination of the environment is avoided.

Furthermore, it is advantageous if the plastic bag has side folds and if the venting openings of the covering strip have at least one distance to the closest welding seam, which distance corresponds to the side fold depth. On the one hand, this can bring about a maximum distance between the venting openings in the wall and the venting openings in the covering strip so that a maximum labyrinth effect is achieved. In addition, the following effect occurs. A filled bag assumes a parallelepipedal shape wherein the side folds are set up and form a side wall. In a corresponding manner, the lower and the upper end areas of the front wall and of the back wall fold over, and form bottom surfaces and head surfaces. If the venting openings now have the indicated distances to the welding seams, they are still in the area of the front wall and of the back wall in the filled bag so that a possibility of venting continues to exist after the bag has been horizontally stored, provided the channel is then arranged on the upper side.

An advantageous embodiment of the invention provides that the plastic bag comprises side folds and that the channel extends over at least one outer corner or an inner corner of one of the side folds. This means that even the cover strip extends over at least one outer corner or over at least one inner corner. This can mean that at least one fastening strip is located on one of the walls of the side folds or that one fastening strip is on the first wall and one fastening strip is on the second wall of the bag. It is advantageous in this embodiment that the channel of the filled bag is located at least partially on one of the side surfaces so that no undesired sealing off the venting opening occurs here by the bag moving in front or by the following bag. In this manner the (slow) venting of the channel is not disturbed, so that the bag can better assume the prescribed parallelepipedal shape before it is palletized. In the variant in which the cover strip extends only over an outer corner, it can be directly placed around said outer corner, wherein an outer corner is also formed in the cover strip. In doing so, the teaching according to the invention is then automatically produced.

The initially cited problem is also solved by a method according to Claim 9. Accordingly, a method for manufacturing and filling of a bag in which

-   -   a roller with a hose web is made available,     -   the hose web is wound off from the roller in a winding-off         device,     -   the hose web is provided with a bottom on its front end in a bag         forming device, preferably by producing a cross wielding seam,     -   a hose piece is separated from the hose web in the bag forming         device,     -   the hose piece is transported by moving holding elements to a         filling device,     -   the bag is filled with a filling material, wherein the air         entering with the filling material into the interior of the bag         is at least partially conducted outward via venting openings in         at least one outer wall of the bag, and     -   the air is conducted into a channel located on the outer side of         a wall,         provides that the volume of the channel is enlarged by the         conducting of air into the channel which covers the venting         openings and which is formed at least by two parallel fastening         strips and by one covering strip, wherein the covering strip         also comprises venting openings, and wherein the shortest path         between the parallel fastening strips is longer along the         covering strip than the shortest path along the at least one         wall between the parallel fastening strips or the covering         strips, and/or the parallel covering strips consist of a         stretchable material.

As a result of the fact that the air is guided into the channel designed according to the invention, the filling material can be filled into the bag at a high speed, wherein the channel can greatly expand. Therefore, the air brought in with the filling material can be guided out of the actual filling material chamber of the bag without it passing into the environment. The latter fact is important since a part of the filling material is often also entrained with a rapid removal of air. According to the invention, air and filling material at first pass into the channel which is used as an intermediate store. From here, the air passes gradually into the environment, wherein the venting performance from the channel into the environment does not have to be very great.

Another advantageous embodiment of the invention provides that after the filling, the bag is transported at least by other movable holding elements to a closing device in which the bag is closed at its second end. Both the transport and the closing can now take place at a high speed since the air introduced with the filling material into the bag interior was now substantially discharged into the channel resulting in a level-oriented head area which can be readily welded by welding devices. Even the optionally still inflated channel is not a problem here, especially in an embodiment in which the channel ends underneath the later head welding seam.

Another embodiment of the method according to the invention provides that the bag is placed on a transport device after the closing at its second end so that the cover strip faces the upper side and/or one of the side surfaces. In this case, the air which is still in the channel can be discharged via the second venting openings, wherein this process can take place slowly. A substantially complete venting must have taken place only, when the filled bags are stacked on a pallet. A little time still passes until the palletizing, which can be used to vent the channel. However, a venting can be designed to be simpler if the channel is in contact with the environment via the venting openings. On the other hand, a venting would not take place rapidly enough if the bag is supported with the channel side on a support surface, e.g., a conveyor belt.

The above-cited problem is furthermore solved by a device for producing and filling bags according to Claim 12. Accordingly, a previously cited device comprising:

-   -   a winding-off device in which a hose web can be wound off from a         roller,     -   a bag forming device in which the hose web can be provided on         its front end with a bottom, wherein a welding device for         producing a transverse welding seal is preferably provided and         in which a hose piece can be separated from the hose web,     -   movable holding elements with which the hose piece can be         transported to a filling device, and     -   a filling device in which the bag can be filled with a filling         material, wherein the air entering with the filling material         into the bag interior at least partially via venting openings in         at least one outer wall of the bag, can be conducted outwards,         wherein the air can be guided into a channel located on the         outer side of a bag wall,         provides that at least one device for facilitating the venting         is provided with which the conducting of the air into the         channel can be facilitated, which channel covers the venting         openings and which is formed at least by two parallel fastening         strips and one covering strip, wherein the covering strip also         comprises venting openings, and wherein the shortest path         between the parallel fastening strips along the covering strip         is longer than the shortest path along the at least one wall         between the parallel fastening strips or the covering strips         and/or the parallel fastening strips consist of stretchable         material, which is advantageous and wherein the volume of the         channel is increased. The term a device for facilitating the         venting therefore means that a component of the production and         filling device according to the invention is designed in such a         manner that it itself or the action which can be carried out by         it is beneficial for the escaping of air into the channel. In         particular, such a device is preferably constructed in such a         manner that it does not influence the channel in its properties.         In other words, the functionality is also given after the action         of the device.

A first advantageous embodiment of the invention provides that the device for facilitating the venting comprises at least one welding beam which is adapted to the contour of the bag in the area of the covering strip. In particular, this can mean that the contour of the at least one welding beam with which either the bottom seam or the head seam can be formed comprises a level surface which, however, comprises a recess in the area in which the channel is located. It is insured in this manner that the channel is not damaged by too high a temperature and/or by too high a contact pressure and/or by a too long welding time. A damage would be, for example, a through melting of the covering strip, which would have the consequence that air and also filling material could pass through the unintended openings into the environment.

Another preferred embodiment of the invention provides a device for facilitating the venting, which comprises at least one transport and/or guide roller the diameter of which, viewed in the axial direction, varies. In particular, it is provided that this transport and/or guide roller comprises a recess which serves to guide the channel. This means that only the areas of the hose walls located outside of the channel rest during transport by the transport or guide roller on its outer surface.

It is advantageous if the device for facilitating the venting in the device according to the invention comprises at least one web guide device with which the hose web can be guided, wherein the hose piece produced from the web comprises a cover strip facing—in the filling station—in the direction of the bag forming device. This web guide device can consist of guide elements such as, e.g., web guide rollers which guide the hose web in such a manner that said features are met. A web guide device can also comprise a winding-off device which comprises a winding-off shaft which can rotate in two directions of rotation. This makes it possible to wind off a hose web roll according to the above-indicated target. In this case, care does not have to be taken that the channel faces in a certain direction, as early as the winding on of the hose web. However, a web guide device can also comprise a turning station which changes the position of the channel when this is necessary. The advantage of the embodiment in which the cover strip faces in the direction of the hose forming device is that a bag which has already been filled and which is arranged in the transport direction in front of the bag to be filled cannot disturb the expansion of the bag to be currently filled. This ensures a good venting of the bag.

An advantageous embodiment of the invention provides that the device for facilitating the venting comprises at least one placing device with which the bag can be placed with its head facing in the transport direction onto a transport device so that the cover strip faces the upper side and/or one of the side surfaces. The device for facilitating the venting can be a thrust element such as, for example a rod, a sheet or even the gripping tongs of the closing station. It is provided here that the thrust element can be moved in the transport direction of the bag and can be moved, at least in the time frame in which it makes contact with the head area of the bag, partially with a transport speed which is greater than the instantaneous transport speed of the bag. The head area of the bag is preferably the upper half of the bag (when the bag is still vertically aligned after the filling), in particular the upper third of the bag. The action of a thrust element or of a similarly acting means causes the bag to be simply thrown over into the transport direction so that it can be transported further in a lying position by a transport device, wherein the main axis of the bag faces in the transport direction. This embodiment makes it possible to arrange the bag on the transport device in such a manner that the channel faces upward and/or to the side so that the air stored in the channel can be expelled via the venting openings of the covering strip, over longer period of time, to the environment without filling material also exiting.

Furthermore, an advantageous embodiment of the invention provides that the device for facilitating the venting comprises at least one agitation device with which the filling material can be set in vibrations. Such an agitation device can be a knocking device which operates with a large amplitude but a low frequency. Alternatively or additionally, this agitation device can be a vibration generator which operates with a rather low amplitude but with a rather high frequency. An agitation device can act on the bag directly or via an intermediate element such as, e.g., a carrier device or a conveyor belt of a transport device. The agitation device is preferably arranged below the filling station so that the filling material can still act on the bag during the filling of the bag or directly thereafter. In this case, the air carried into the bag with the filling material can escape into the channel. An agitation device is also advantageously arranged in the area of transport devices on which a bag rests after the closing. In this case, residual air inside the bag can still escape into the channel and then into the environment.

Other advantages, features and details of the invention are apparent from the following description in which various exemplary embodiments are explained in detail with reference made to the figures. The features mentioned in the claims and in the specification can be significant for the invention individually or in any combinations of cited features. In the framework of the entire disclosure, features and details described in conjunction with the method according to the invention of course also apply in conjunction with the device according to the invention and vice versa so that as regards the disclosure of the individual aspects of the invention, reciprocal reference is made or can be made. The same applies regarding the disclosed features of a bag according to the invention which also apply in any combination with the features of the method according to the invention and/or of the device according to the invention and/or vice versa. Even features which are described or were described in conjunction with other features can also be features according to the invention, even independently of these other features alone or in combination with any other features. Reciprocal reference can also be made to these feature combinations. In the individual figures:

FIG. 1 shows a section through a first embodiment of a bag according to the invention,

FIG. 2 shows a section through another embodiment of a bag according to the invention,

FIG. 3 shows a section through another embodiment of a bag according to the invention,

FIG. 4 shows a section through yet another embodiment of a bag according to the invention,

FIG. 5 shows a section through another embodiment of a bag according to the invention,

FIG. 6 shows a view of a step for producing a bag according to the invention,

FIG. 7 shows another view of a step for producing a bag according to the invention,

FIG. 8 shows yet another view of a step for producing a bag according to the invention,

FIG. 9 shows a longitudinal section through an embodiment of a bag according to the invention,

FIG. 10 shows a longitudinal section through another embodiment of a bag according to the invention,

FIG. 11 shows a basic sketch of a first embodiment of an FFS system according to the invention,

FIG. 12 shows a basic sketch of a first embodiment of another FFS system according to the invention,

FIG. 13 shows a view of a structural component in an FFS system according to the invention, and

FIG. 14 shows a view of a roller in an FFS system according to the invention.

FIG. 1 shows the cross section through a first embodiment of a plastic bag 1 according to the invention. It comprises a first wall 2 which represents the back wall in the present example. This first wall is connected by the side folds 3, 4 to the second wall 5 which represents the front wall. The side folds 3, 4 each comprise two side fold walls 6′ and 6″ and 7′, 7″, respectively, wherein the side fold walls 6′ and 7′ are connected to the second wall 5 by outer edges 8′ and 9′, respectively, and the side fold walls 6″ and 7″ are connected by outer edges 8″ and 9″, respectively, to the first wall 2. The side fold walls 6′ and 6″ and 7′, 7″, respectively, are connected to one another by inner edges 9 and 10.

The front wall 5 is formed by a first area 11 and a second area 12. The edge 13 of the first area 11 is fastened by a fastening strip 14 to the surface facing the bag interior 15. The strip extending over the fastening strip 14 forms a cover strip 16 which covers the vent holes 17 of the second wall 5. The cover strip 16 is connected to its edge 18 by a fastening strip 19 on the outer surface of the first area 6 of the second wall 5. The cover strip 16 is fastened here by its outer surface to the first area 6 so that a U-shaped fold 20 or, in the flat state, a double-layer area of the cover strip is formed. In this manner, a channel 21 is formed the volume of which can be varied within a very large range. Furthermore, this channel comprises venting holes 22 so that the air which passed from the bag interior into the channel can escape into the environment.

The cover strip 16 can be delimited from the area 12 of the front wall 5 by the fastening strip 14.

A filter material 23 is preferably provided on the surface, facing the channel, of the cover strip 16, which filter material is fastened to the cover strip by two fastening strips 24.

FIG. 2 shows another exemplary embodiment of a plastic bag 1 according to the invention. Instead of the U-shaped fold of the cover strip 16, in this exemplary embodiment a z-shaped fold 26 is provided which is produced in that a double folding is produced. The z-shaped folding is distinguished in that three layers are formed in it. Even if it can be recognized in FIG. 2 that the z-shaped fold 26 is arranged in the area of the fastening strip 19, the -shaped fold can be arranged at any position between the fastening strip 14 and the fastening strip 19. Even several z-shaped folds 26 are conceivable.

In the embodiment of FIG. 3, the cover strip 11 of the valve bag 1 even comprises a z-shaped fold 21 and a U-shaped fold 15.

The features of the exemplary embodiments according to FIGS. 1 to 3 can be combined in any manner with each other. However, it is important in all instances that the length of the path which is set by the line of the cover strip 16, visible in the figures between the fastening strip 14 and the fastening strip 19, is longer than the length of the path which is set by the line of the second wall 5 visible in the figures between the fastening strip 14 and the fastening strip 19. It is preferable here if the difference in length is at least 3%.

FIG. 3 shows another possible embodiment which can also be combined with all other exemplary embodiments disclosed in this patent application. In this case, the covering strip 16 is fastened by a third fastening strip 27 to the area of 11 of the front wall 5. This third fastening strip 27 divides the channel 16 into a first partial channel 28 and a second channel 29, wherein the venting openings 17 run from the bag interior 15 into the first partial channel 28. The venting openings 22 run from the second partial channel 29 into the environment. In order that the air can pass out of the first partial channel 28 into the second partial channel 29, the fastening strip comprises at least one interruption. Preferably, the at least one interruption is so long that the venting performance of the bag is not adversely affected.

In the exemplary embodiment according to FIG. 4, in contrast to the exemplary embodiments according to FIGS. 1 to 3, the covering strip 16 is formed as a separate work piece. Accordingly, it is not constructed in one piece with a part of the front wall 5. This separate covering strip 16 is fastened by the two fastening strips 14, 19 to the front wall 5 of the valve bag. It is shown as an example that the cover strip 16 comprises U-shaped folds 20 on its two edges. The front wall 5 and the back wall 2 of the plastic bag 1 can have been already produced as hose, for example, by a blow foil extrusion method or a round web method. However, a hose can also have been produced from a flat web in which the two side areas were folded back, forming an overlapping and in which the overlapping edges are connected by a joining seam.

FIG. 5 shows another exemplary embodiment in which the cover strip 16 extends over the outer corner 8′. The fastening strip 14 is located on the front wall 11 whereas the fastening strip 19 is arranged on the side fold wall 7′. The venting openings 17 can be arranged in the side fold wall 7′, as is shown in FIG. 5. The cover strip can also extend over another or over several outer corners. As regards the U- and/or Z-shapes of the edges, the cover strip can be designed according to one of FIGS. 1 to 4 or to a combination of them. However, it is also possible in the present exemplary embodiment to provide, in a deviating manner, no U- or z-shaped folding over but instead to provide a folding over in the area of the outer corner 8′ which, however, is at a distance from the latter so that the path according to the invention is longer between the fastening strips along the cover strip than along the front wall and the side fold wall 7′.

FIG. 6 shows a few steps of a method according to the invention for producing a plastic bag. To this end, a flat web 50 is at first wound off from a winding-off device which is not shown. Subsequently, the introducing of venting openings, which is again not shown, takes place, of which a few venting openings 22 are sketched in by way of example. These venting openings are preferably not added in a longitudinal direction of the flat web in a continuous manner but rather in a cycled manner. To this end, a roller can roll off on the flat web, the circumferential surfaces of which roller is covered only partially with needle tools, cutting tools or stamping tools.

Alternatively or additionally, it can be provided that such a roller can be brought in contact with the flat web 50 at the positions at which venting openings 22 are to be introduced. To this end, a positioning mechanism can be provided which brings the roller in contact with the flat web in a cycled manner. In doing so, the flat web preferably runs over a counter roller.

The venting openings 17 can be introduced into the flat web 50 in the same manner. However, in this case a roller 51 is shown with which individual, short steps are produced in the flat web 50. The circumferential surface 52 of the roller 51 is additionally provided with knives 53, wherein each two adjacent knives can enclose an angle to one another, in particular a right angle. A positioning mechanism can also be provided for the roller 51 and which brings the roller in contact with the flat web in a cycled manner. The positioning mechanism for the roller 51 operates independently of the positioning mechanism mentioned in the previous paragraph since the venting openings 12 and 17 are introduced preferably offset in the transport direction of the flat web.

After the introduction of the venting openings 17 and before or after the introduction of the venting openings 22, the flat web 50 can be covered with a filter material 55 which is fastened on the flat web 50. This filter material can be applied in web form on the flat web.

To this end, the filter material can be made available as a roll and wound off inside a rolling-off device. It can be provided for the fastening of the filter material that the filter material is provided already in its roll form with two lateral adhesive strips. However, it is advantageous if two adhesive tracks 56, 57 are applied on the flat web and/or on the web-shaped filter material, wherein the venting openings 17 are located completely inside these adhesive tracks. The adhesive tracks can comprise a dispersion adhesive, a hot-melt adhesive or a cold glue; however, they can also comprise an extrudate. In the latter case, plastic is transferred in an extruder into a molten form and applied in this form by nozzles as tracks. The flat web and the web-shaped filter material are preferably joined together immediately after the application of the adhesive tracks, which is indicated by the arrows 58, and pressed against one another—for example by a pair of press rollers which are not shown—and optionally also cooled.

In another embodiment the filter material 55 can also be applied on the flat web in a card form, wherein the filter material is dimensioned at least in such a manner that it completely covers the venting openings 22 concentrated on a surface section. In order to make the filter material available in form of a slip of paper, already manufactured slips can be used. However, it is preferable if the filter material is also present here in a roll form and is individualized by an individualizing tool, for example, by a cutting tool, to slips. The adhesive tracks are now preferably applied on the flat web 50, wherein a circumferential adhesive track is produced in order that the air, which should pass through the filter material, cannot escape through a gap in the adhesive track.

The described procedures for applying filter material can also be used if the venting openings 17 are to be covered with a filter material.

FIG. 7 shows the folding over of the side areas of the flat web 50, wherein the side folds 3 and 4 according to FIG. 1 are simultaneously added and wherein the back wall 2 and the two areas 11 and 12 of the front wall 5 are formed. It is advantageous here if the area 11 has already been folded over further at a fixed position than the area 12. The U-fold 20 is preferably produced as early as before or also during the folding over of the area 12. Even alternative or additional folds can now be added in. However, it is possible that the described folds can be added even after the folding over of the areas 11 and 12.

FIG. 8 shows the already folded-over areas 11 and 12, which are now fastened to one another by the fastening strips 14 and 19. To this end, two extrusion nozzles are in an advantageous embodiment which add at least one molten plastic material in the form of at least two parallel tracks between the areas 11 and 12 and limit the channel 21 in this manner. The areas 11 and 12 along the fastening strips 14 and 19 can be connected to one another with at least one pressing device, for example a pressure roller which is not shown so that a durable and lasting connection can be produced. At least one cooling device can be provided in order to be able to cool off the fastening strips, especially if they were produced under to action of heat. The cooling device can be comprised by the pressing device. In this manner, for example, pressure rollers can be cooled.

The method steps which were explained using the FIGS. 6 to 8 can be carried out with a hose forming device which can form, together with a device according to the invention, a system for forming plastic bags from flat web material.

FIG. 9 shows a bag 101 produced in the FFS method—designated in short as “bag”, which is preferably produced from a hose according to the exemplary embodiments of FIGS. 1 to 7. In order to produce a bag 101 from such a hose, this hose is at first provided on its leading edge with a welding seam 120—the so-called bottom welding seam, which runs transversely to the direction of the main extension of the bag 101 (transverse welding seam) and is subsequently individualized from the hose to a hose piece with the desired length so that an upper, non-closed bag is produced. The hose piece is now brought to a filling station by transport parts which grasp in the area of the upper end of the bag, for example, transport grippers. In the filling station, the non-closed end of the bag is opened so that a filling opening is produced through which the filling material can be filled in. The bag is held by holding parts—grasping pincers are also advantageous here—in the filling station and in particular during the filling. After the bag has been filled, it is brought to the closing station, among other things, by other transport parts which again grasp in the area of the upper end of the bag, in which closing station a welding seam 121 is produced on the upper and of the bag in order to close the bag. This welding seam, which can also be designated as a head welding seam, is also a transverse welding seam.

It can be recognized that the second wall 5 continues up to the welding seams and past them. The wall 5 comprises, as already explained, the channel 21 which is limited by the fastening strips 14 and 19, which are not visible here. Furthermore, it can be recognized that the venting openings 22 are arranged closer to the bottom without valves that the venting opening 17. The distance of the venting opening 22 to the bottom 102 is preferably a maximum of one third, preferably a maximum of one fourth, in particular of one fifth of the entire bag length L. The term bag length L denotes the shortest distance between the welding seams 120 and 121 when the bag 101 has not yet been filled and the walls 2 and 5 still have at least a partial touching contact with one another.

Conversely, it is provided that the venting openings 22 are arranged closer to the head welding seam 121 than the venting opening 17. The distance of the venting openings 12 to the welding seam 121 is preferably a maximum of one third, preferably a maximum of one fourth, and in particular a fifth of the entire bag length L. On account of the previously cited arrangement and in particular the distance of the venting openings relative to each other, the escaping air must traverse a long path inside the channel 21, as a result of which its flow rate is reduced so that an entrainment of filling material is reduced.

FIG. 10 shows another embodiment of a bag according to the invention. This embodiment is similar to the embodiment according to FIG. 9. However, the difference is that the covering strip 16 does not run to the bottom welding seam 120 and/or to the head welding seam 121 but rather terminates with its one end in the area between the venting openings 22 and the bottom welding seam 120 and with its other end between the venting openings 17 and the head welding seam 121. In this exemplary embodiment the ends of the covering strips are preferably fastened on the wall 5 by other fastening strips 130, 131 in order to bring about a sealing of the channel 21 against the environment. The fastening strips preferably run transversely to the longitudinal extension of the bag 101.

FIG. 11 shows a basic sketch of an FFS system 200 according to the invention. This FFS system is provided for producing, filling and closing bags with a filling weight of more than 5 kg.

At first, a wound-up hose 201 in the form of a winding 202 is wound off in a winding-off device 203. The winding off in the winding-off direction R is brought about in particular by a forward traction roller pair 204 from which at least one of the two forward traction rollers can be driven in a rotary fashion by a drive. A web storage device—preferably in the form of a compensating device—can be provided directly in front of or directly in the back of the forward traction pair so that the cyclic forward traction of the hose required in the FFS system can be carried out even if the hose is drawn off from the winding with a substantially constant speed.

The cover strip 16 is symbolized by the wavy line 205, wherein it is important here that it is arranged at the shown position on the upper side of the hose. In other words, the cover strip is arranged on the outer side of the hose wound up on the winding.

The forward traction roller pair 204 and the optionally following compensating device can be followed by a first welding device 206 in the transport direction of the hose with which, for example, corner flame washings, supplementary transverse welds which cover the hose entirely or partially in its width, and/or also longitudinal welds of the hose can take place. In the further course, viewed in the transport direction, a cooling device 207 can now be provided with which the produced welding connection can be cooled off again. Instead of or in addition to the welding device and/or cooling device, even other processing devices such as, for example, a perforation device and/or a stamping device can be provided which can provide the hose with perforations or stampings for a better handing of the subsequent bag.

A deflection roller 208 follows, which now guides the hose to a registering device consisting of two other rollers 209 and 210. To this end, the rollers 209 and 210 can shift relative to one another so that by a changing of the running path of the hose, the position of welding seams perforations, stampings but also impressions or other regularly occurring properties of the hose can be compensated with following processing devices.

After having been guided over another deflection roller 211, the hose is guided by another forward traction roller pair 212 into a combined transverse sending and individualizing device 213. This device 213 comprises—viewed in the direction of advance—at first a transverse welding device for producing a bottom seam on the hose. A transverse separating device follows underneath this transverse welding device, with which transverse separating device a hose piece—on which a transverse welding seam had been attached in the processing cycle located timewise directly previously—separates from the hose. Non-shown transport parts grasp the hose piece as early as prior to the separation and bring it, also optionally by other transport means, into the filling station 214.

Holding parts are located in the filling station which hold the hose piece or the bag 101 fast so that it remains in a substantially vertical position during the filling. Opening means, which are also not shown, can serve to open the filling opening of the bag so that a filling funnel 215 can be introduced into the bag interior. Subsequently, the filling of the filling material into the bag is possible, which is indicated by the arrow 216. During the filling, the bag can rest on a support device so that the bottom welding seam which has possibly not yet completely cooled off, is not too heavily stressed. In the exemplary example shown, the support device is shown as transport means 217 which is also provided for the further transporting of bags to following stations in addition to the support function. Furthermore, at least one agitation and/or knocking device is provided which can act on the bag from the outside in order to hereby put it in motion, for example, in vibrations. This agitation and/or knocking device can be integrated in the support device. The filling material can be compressed by the agitation and/or knocking device. This means that air that is still located inside the filling material exits and escapes, for example, through the venting openings.

The filled bag is moved in transport direction Z by the transport means 217, wherein non-sketched transport means, preferably grippers, hold the bag at the upper end in order to secure the bag, on the one hand, against falling down and to hold the two walls in touching contact so that a defined head welding seam can be applied. This head welding takes place in the closing station 218. The welding tool is symbolized by the two arrows 219. The arrows indicate the direction of movement of parts of the welding tool.

The closing station 218 can optionally also be followed by a cooling station 219 which is constructed similarly to the closing station but—instead of welding tools—comprises cooling tools in order to cool the welding seam produced for closing the bag and to therefore make it immediately loadable.

In the further course, the bag, which is still arranged upright, is transferred into a lying position, as is indicated with the bag 101′. Here, an element of the FFS system acts on the head area so that the latter is moved at a lower speed in the transport direction Z, as the bottom area moved further by the transport means. This has the consequence that the bag 101′ is transported in the further course with the bottom advancing in front. Accordingly, the cover strip as well as the venting openings are on top, that is, on the bag wall facing away from the transport means 217. In this manner, the venting of the bag continues to be ensured in case the air carried in with the milling material has not yet completely escaped.

The described speed difference can be produced in that, for example, the welding tools, cooling tools and/or transport parts have not yet completely released the bag while the transport means is already moving the bag further. Alternatively, a rod 220 can be provided which runs in the transverse direction and is arranged, for example, firmly in the FFS system.

In this exemplary embodiment shown in FIG. 11, the cover strip of the bag, viewed in transport direction Z, is arranged on the leading wall. This embodiment can be readily realized regarding the subsequent transport position with “bottom in front” since no separate, moving machine element is needed. However, care should be taken that the filling station 214, the closing station 218 and the cooling station have a sufficient distance from each other so that a leading bag does not touch the directly following bag so strongly that the cover strip is pressed flat. In this case the venting quality would be ineffective.

In the alternative exemplary embodiment of FIG. 12 the hose is wound off in a winding-off direction R′ which is opposite in comparison to the FIG. 11 so that the cover strip, again represented here by the wavy line 205, is now located on the bottom of the hose. Alternatively, the winding-off direction R according to FIG. 11 can also be provided and the winding can be used onto which the hose is wound up in such a manner that the cover strip faces inward. Both named measures have the consequence that—in particular in the filling station—viewed in the transport direction Z, the following wall carries the venting strip so that the latter can expand in the filling station unhindered by other bags in order to receive the greatest possible volume of air.

The FFS system itself is unchanged in comparison to FIG. 11 up to and including the cooling station 219. Therefore, the reference numerals and the description parts of FIG. 11 can be transferred onto FIG. 12 but is refrained from, for the sake of clarity. However, it is necessary in an FFS system 200 according to FIG. 12 to accelerate the bag by its head end in order to bring it into a lying position onto the transport means with a leading head seam. In addition, a rod 220 can be suspended in a rotating device. For example, it can be arranged eccentrically on a rotary disk the axis of rotation of which runs parallel to the direction of the extension of the rod 220. Therefore, the rod 220 can carry out a movement in the direction of arrow 221 and therefore—assuming a sufficiently high speed of rotation—accelerate the head area of the bag. However, even numerous embodiments are possible here which, however, are all comprised by the present inventive idea.

FIG. 13 shows a structural component 300 which can be set inside an FFS system 200 in order to ensure a reliable operation even when processing hoses with cover strips. This structural component can be the cheeks of a welding device with which, for example, heat- and/or bottom welding seams can be put on the hose, a piece of the hose and/or a bag. Structural parts of the structural component are the two cheeks 301 in 302, which are, for example, heated welding cheeks. The cheek 302 is provided with a recess 303 which is coordinated with the position of the cover strip. This brings it about that the cheek 302 is loaded with the same heat transfer on all parts of the wall to be loaded with the heat so that an orderly formation, for example, of the welding seam takes place. If the cheek 302 did not have this recess, it could occur that the cover strip is welded through and therefore destroyed whereas other areas of the wall do not receive any sufficient heat for a welding. The cheeks can also be a structural part of a cooling device inside the FFS system.

FIG. 14 shows a roller 400 which can be provided as a deflection roller, transport roller, conveyor roller, forward traction roller and/or guide roller in an FFS system according to the invention. An area of 401 is provided with a diameter which is smaller than the diameter of the other areas 402. In order to produce such a roller 400, at first, the roller body can be produced with a uniform diameter over the roller length. Subsequently, a chip-removing processing can take place in the area 401, for example, by turning or milling A roller 400 can be provided in a likewise advantageous embodiment the roller body of which has a uniform diameter over the entire length of the roller, wherein, however, casings can then be pushed onto areas of the roller body. These casings then form the areas 402. In this manner, the position of the area 401 can be moved in an axial direction and/or the width of the area 401 can be varied by shifting and/or replacing casings. The roller 400 is rotatably supported by pins 403 in the machine frame or its added parts of the FFS system.

A roller 400 is preferably provided at such positions inside the FFS system at which the hose must be guided in such a manner that the cover strip faces the roller surface. It can occur—when using a traditional roller with a constant diameter over its length—that the hose runs sideways due to the uneven contact surface. This is avoided by providing a roller 400.

List of reference numerals  1 Plastic bag  2 First wall  3 Side fold  4 Side fold  5 Second wall  6 Side fold wall 7 7′ Side fold wall 8 8′ Outer edge 9 9′ Inner edge  10 Inner edge  11 First area  12 Second area  13 Edge of the first area 11  14 Fastening strip  15 Bag interior  16 Cover strip  17 Venting openings  18 Edge of the cover strip  19 Fastening strip  20 U-shaped fold  21 Channel  22 Venting opening  23 Filter material  24 Two fastening strips  25  26 z-shaped fold  27 Third fastening strip  28 First partial channel  29 Second partial channel  30  31  50 Flat web  51 Roller  52 Circumferential surface  53 Knife  55 Filter material  56 Adhesive track  57 Adhesive track 101 Bag 120 Welding seam 121 Welding seam 130 Fastening strip 131 Fastening strip 201 Wound-up hose 202 Winding 203 Winding-off device 204 Forward traction roller pair 205 Wavy line 206 First welding device 207 Cooling device 208 Deflection roller 209 Roller 210 Roller 211 Deflection roller 212 Forward traction roller pair 213 Individualizing device 214 Filling station 215 Filling funnel 216 Arrow indicating the filling of the filling material into the bag 217 Transport means 218 Closing means 219 Arrow symbolizing the welding tool 220 Rod 221 Arrow 300 Structural component 301 Cheek 302 Cheek 303 Recess 400 Roller 401 Area 402 Areas 403 Pin 

1. A plastic bag, in particular an FFS bag, comprising a first wall and a second wall which are connected to one another by side edges or side folds and by bottoms and bound a bag interior, wherein at least one bottom comprises a weld seam which runs between the side edges and contacts them, and comprising vent openings in the first and/or in the second wall for venting the bag interior, characterized in that at least one channel is provided on the outside of at least one wall which channel covers the vent openings and which is formed at least by two parallel fastening strips and a cover strip, wherein the cover strip also comprises openings and wherein the shortest path between the parallel fastening strips along the cover strip is longer than the shortest path along the at least one wall between the parallel fastening strips or the cover strips and/or the parallel fastening strips consist of stretchable material.
 2. The plastic bag according to claim 1, characterized in that the shortest path between the parallel fastening strips along the cover strip is at least 3% longer than the shortest path along the at least one wall.
 3. The plastic bag according to claim 1, characterized in that a layer of a filter material is provided inside the channel.
 4. The plastic bag according to claim 1, characterized in that a layer consisting of a filter material is provided in the bag interior, wherein the filter material covers the venting openings.
 5. The plastic bag according to claim 1, characterized in that the air permeability of the venting openings in the at least one wall is greater than the air permeability of the cover strip.
 6. The plastic bag according to claim 1, characterized in that the venting openings of the cover strip are at a distance from at least one bottom by a maximum of one half a bag length, in particular by a maximum of one third of the bag length.
 7. The plastic bag according to claim 1, characterized in that the plastic bag comprises side folds and in that the venting openings of the covering strip have at least one distance to the closest welding seam, which distance corresponds to the side fold depth.
 8. The plastic bag according to claim 1, characterized in that the plastic bag comprises side folds and in that the channel extends over at least one outer corner or inner corner of the side fold.
 9. A method for manufacturing and filling a bag, in particular a bag according to claim 1, wherein a roller with a hose web is made available, the hose web is wound off from the roller in a winding-off device, the hose web is provided with a bottom on its front end in a bag forming device, preferably by producing a cross wielding seam, a hose piece is separated from the hose web in the bag forming device, the hose piece is transported by moving holding elements to a filling device, the bag is filled with a filling material, wherein the air entering with the filling material into the interior of the bag is at least partially conducted outward via venting openings in at least one outer wall of the bag, and wherein the air is conducted into a channel located on the outer side of a wall, characterized in that the volume of the channel is enlarged by the conducting of air into the channel which covers the venting openings and which is formed at least by two parallel fastening strips and by one covering strip, wherein the covering strip also comprises venting openings, and wherein the shortest path between the parallel fastening strips is longer along the covering strip than the shortest path along the at least one wall between the parallel fastening strips or the covering strips, and/or the parallel covering strips consist of stretchable material.
 10. The method according to the previous claim, characterized in that after the filling, the bag is transported at least by other movable holding elements to a closing device in which the bag is closed at its second end.
 11. The method according to the previous claim, characterized in that the bag is placed on a transport device after the closing at its second end so that the cover strip faces the upper side and/or one of the side surfaces.
 12. A device for producing and filling a bag, in particular for carrying out a method according to claim 1, comprising: a winding-off device in which a hose web can be wound off from a roller, a bag forming device in which the hose web can be provided on its front end with a bottom, wherein a welding device for producing a transverse welding seal is preferably provided and in which a hose piece can be separated from the hose web, movable holding elements with which the hose piece can be transported to a filling device, and a filling device in which the bag can be filled with a filling material, wherein the air entering with the filling material into the bag interior at least partially via venting openings in at least one outer wall of the bag, can be conducted outwards, wherein the air can be guided into a channel located on the outer side of a bag wall, characterized in that at least one device for facilitating the venting is provided with which the conducting of the air into the channel can be facilitated, which channel covers the venting openings and which is formed at least by two parallel fastening strips and one covering strip, wherein the covering strip also comprises venting openings, and wherein the shortest path between the parallel fastening strips along the covering strip is longer than the shortest path along the at least one wall between the parallel fastening strips or the covering strips and/or the parallel fastening strips consist of stretchable material, wherein the volume of the channel is increased.
 13. The device according to the previous claim, characterized in that the device for facilitating the venting comprises at least one welding beam which is adapted to the contour of the bag in the area of the covering strip.
 14. The device according to claim 12, characterized in that that the device for facilitating the venting comprises at least one transport and/or guide roller the diameter of which, viewed in the axial direction, varies.
 15. The device according to claim 12, characterized in that the device for facilitating the venting comprises at least one web guide device with which the hose web can be guided, wherein the hose piece produced from the web comprises a cover strip facing in the filling station in the direction of the bag forming device.
 16. The device according to claim 13, characterized in that the device for facilitating the venting comprises at least one placing device with which the bag can be placed with its head facing in a transport direction onto a transport device so that the cover strip faces the upper side and/or one of the side surfaces.
 17. The device according to claim 13, characterized in that the device for facilitating the venting comprises at least one agitation device with which the filling material can be set in vibrations. 